Absorption refrigerated column

Fig. 2.35. Schematic drawing of an absorption refrigeration plant based on information from Deutsche Babcock-Borsig AG, D-l 3500 Berlin and ALD Vacuum Technologies GmbH, D-63526 Erlensee, Germany. 1, Expulsion of NH3 from the water-NH3 solution 2, rectification column for NH3 3, NH3 condenser ...

Refrigerated columns may suffer from water accumulation. Using absorption oil instead of refluxing column can solve problem. 

Industrial analysis of hydrocarbon gases 25 years ago was limited almost to Orsat-type absorptions and combustion, resulting in crude approximations and inadequate qualitative information. The more precise method of Shepherd (56) was available but too tedious for frequent use. A great aid to the commercial development of hydrocarbon gas processes of separation and synthesis was the development and commercialization of high efficiency analytical gas distillation units by Podbielniak (50). In these the gaseous sample is liquefied by refrigeration, distilled through an efficient vertical packed column, the distillation fractions collected as gas and determined manometrically at constant volume. The operation was performed initially in manually operated units, more recently in substantially automatic assemblies. 

The refrigeration unit is responsible for cooling both the make-up water and the top-section cooling-coil water (in the absorption column) to 7°C. Make-up water available at 20°C is taken from the deionized-water loop. 

Figure 9.40 outlines the process licensed by ELTECH Systems. Compressed gas at about 7 bar is cooled first with water and then with a refrigerant to—lOor—15°C. When this process follows a low-severity liquefaction system, this step alone can recover much of the chlorine. After removal of the liquid, the gas then passes up through an absorption column against cold CCI4. The noncondensable gases leave the absorption system under... 

The flow diagram of the absorption scheme is shown in Fig. 4. An ammonia/water refrigeration cycle is used both to boil up the bottom column outlet stream and to condense the top column outlet stream. 

The feed gas is first chilled by heat exchange with process off-gas streams and then by ammonia refrigeration to a temperature between -30 and -SS°F. The feed gas then passes to the piewash and absorber column. The prewash and absorber column is divided into three major sections the bottom prewash, the middle main absorption, and the top final absorption sections. The middle main absorption section is divided into upper and lower. segments by a chimney tray. The bottom or prewash section removes naphtha and other relatively heavy impurities, while H2S, CO2. and most of the lighter impurities are absorbed in the middle main absorption sections. The top final absorption section removes the residual traces of CO2 and H2S from the product gas. Methanol is used in all three sections to accomplish these separations. 

The leanest methanol, from the hot regenerator colunm, is fed to the top final absorption section of the prewash and absorber colunm. Most of the methanol from the flash regenerator is returned to the upper main absorption section. Methanol from this upper main absorption section is withdrawn from the prewash and absorber column and chilled by ammonia refrigeration. Most of this methanol is recycled back to the top tray of the lower main absorption section. This removes the heat of absorption and permits higher solution loadings. A small slipstream of the rich, chilled methanol is used for heavy impurity removal in the bottom prewash section. 

FIGURE 11.20 Technological scheme for the purification of natural gas from sulphur components with concurrent production of methanol by the DMTM (1) gas compression and heating unit, (2) reactor unit, (3) air compression unit, (4) separation unit, (5) rectification unit, (6) receptacle for methanol, (7) receptacle for vat residue, (8) ammonia refrigerator, (9) absorption column, (10) raw gas source, (11) regeneration column, (12) hydrogen sulphide utilization unit, (13) pump, (14) sweet gas consumer. 

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